If a rotating machine (a rotating electrical machine) such as a motor or a generator suddenly fails due to a bearing damage or the like, an unplanned repair action or exchange is required. Then, a sudden failure of the rotating machine causes lower availability of the production facility or a readjustment of the production plan. Conventionally, a rotating machine has been stopped as appropriate to diagnose the rotating machine in an offline state for checking a degradation state of the rotating machine. Such a diagnosis may allow for preventing a sudden failure, but requires the rotating machine to be stopped for the offline diagnosis. For this reason, such a diagnosis method causes lower availability of the production facility.
In view of such a background, there is a growing need for an online diagnosis that allows for diagnosing a rotating machine in operation.
For example, an online diagnosis method for a rotating machine is disclosed in Japanese Patent Application Publication No. H11-83686. The diagnosis method for a rotating machine disclosed in Japanese Patent Application Publication No. H11-83686 calculates a diagnosis parameter based on a power frequency of a motor and a high frequency spectrum of a load current signal spectrum of the motor. Then, the method compares the calculated diagnosis parameter with a criterion value set in advance for each mechanical equipment to be diagnosed, and if the calculated diagnosis parameter is larger than the criterion value, the mechanical equipment is judged to be in error. That is, the technique disclosed in Japanese Patent Application Publication No. H11-83686 diagnoses an anomaly of a rotating machine based on the peak in a specific frequency component.